Fuel rods for nuclear reactors are prepared by filling cylindrical metal cladding with nuclear fuel pellets. When the activity of the fuel has declined to the point where the fuel rod is no longer efficient, the rod is removed from the reactor and the fuel is separated from the cladding for reprocessing. Many processes have been reviewed for separating the fuel from the cladding including dissolving the cladding in sulfuric acid or molten metal, melting the cladding, simultaneously dissolving the cladding and the core and simultaneously cutting and dissolving the core.
Current reprocessing technology uses a shear and leach process. In this process, individual fuel rods are fed into a shear where the rods are chopped into three inch segments. These segments are then transported to a chemical leacher where hot nitric acid is continuously recirculated over the sheared segments, dissolving the fuel. The cladding hulls are removed for washing, inspection, and releaching if all the fuel has not been dissolved. Separating the fuel from the cladding by dissolution takes from two to four hours for oxide fuels and approximately 24 hours for metal fuels. All solutions used to wash or releach the cladding are added to the fuel solution for further separation.
While the shearing and leaching process has been successfully used in the reprocessing of light water reactor fuel, its application to the reprocessing of liquid metal fast breeder reactor fuels is complicated by high rates of decay heat generation which requires cooling, the release of fission gases, the difficulty in containing fine core and clad particles during shearing, and the presence of liquid metal coolants such as sodium, which may react violently with hot nitric acid.